Method of making a roughened tow



Nov. 6, 1962 J. H. KEEN 3,0

METHOD OF MAKING A ROUGHENED TOW Filed Oct. 26, 1959 All? 8 SOLVENT OUT APPLIED AT T H/S POINT ROLL JAMES h! KEEN INVFJVTOR.

BY%M,M fl w-MM ATTORNEYS United States Patent 3,062,611 Patented Nov. 6, 1962 3,062,611 METHUD OF MAKING A ROUGHENEDTOW James H. Keen, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Oct. 26, 1959, Ser. No. 848,606 4 Claims. (Cl. 18-54) This invention relates to the production of new filaments and especially roughened filaments. More particularly, this invention concerns a process of producing roughened filaments, which filaments may be of a rela addition, the roughening of filaments has other uses.

A number of ways have already been suggested for applying fine particles to filaments. For example, it has been suggested to blow the fine particles onto the freshly spun filaments as the filaments emerge from the spinneret. However, such method is not too satisfactory. Frequently it is not possible to apply sufiicient of the particles. Any surplus particles blowing over into the solvent recovery process may cause difliculties. Various other ways have been suggested and several of the presently used methods involve the addition of the additive particles to the finished filaments being used in the filter manufacture. While such methods are operable, they may be relatively expensive or present some degree of inconvenience since the operation is performed by the filter manufacturer rather than the manufacturer of the filaments.

In addition, there is the long standing problem of causing the particles to adhere sufficiently strongly to the filaments so that the particles will not dust off. It is thought readily apparent that if the particles separate from the filaments during flexing and inter-fiber movement, this is not satisfactory. Also, it is apparent in the case of a tobacco smoke filter that separation of additive is undesirable not only because of loss of filter efficiency, but due to the unpleasantness and distastefulness to the smoker that may arise if such materials get into the smokers mouth or respiratory system.

Accordingly, it is believed apparent that the development of a method for preparing filaments carrying an additive on their surface, particularly relatively small filaments, which method is adaptable to use during filament manufacture, represents a highly desirable result.

After considerable investigation, I have found a method for roughening filaments which is relatively simple and economical and which may be accomplished relatively early in the manufacture of tow. I have further found how to prepare a new combination comprised of a bundle of especially fine denier filaments which filaments may carry a rou hening agent.

This invention has for one object to provide a method for producing rough surfaced filaments and particularly roughened surface cellulose acetate filaments. A further object is to provide a method of the type indicated which avoids the use of dry or dusty finely divided particles for obtaining the roughened surface. A special object is to provide a method for the manufacturing of very fine denier filaments which may be roughened by the procedures of the present invention. Still another object is to provide a method for the manufacture of tows of filaments made up of fine denier filaments and of'various .types of filaments which have a roughened surface. .A

still further object is to provide filament tows which have particular utility for the manufacture of tobacco smoke filters. Other objects will appear hereinafter.

In the broader aspects of my invention I have found that liquid slurries of certain compositions may be applied to the freshly spun filaments. These freshlyspun filaments may be of the conventional prior art type produced by conventional prior art processes. However, in

certain preferred embodiments of the present invention 1 wouldproduce a relatively fine denier filament by certain novel procedure which will be described hereinafter.

As apparent, the liquid application of a slurry in accordance with the present invention avoids the problems of dusting and the like encountered in the prior art procedures. Also, the liquid application of the special slur- ;ries of the instant invention permits the applying of larger quantities of additive to filaments as will be observed .from the disclosure which follows.

The filaments treated with liquid slurries of certain polymers in accordance with the present invention are then passed through further steps for making the treated filaments into a tow. Certain of these further steps are to be applied in any event and, therefore, the utilization of the present invention does not increase manufacturing cost. These further steps convert the slurry into a form whereby bonded particles are formed on the surface of the filaments to give the roughened filaments of the present invention.

In further detail in my proposed novel method for making a rough-surfaced filament, fine particles of a polymer having a low melting point are dispersed in a water solution to form a slurry which is applied by a method to be disclosed in detail hereinafter. The filaments thus treated with the slurry are then crimped and passed through a tow drier or suitable heating device to raise the temperature of the filaments. The temperature is raised to the softening or melting point of the aforesaid low-melting polymer, where it softens and bonds to the surface of the filament. This melt-bond of the particle is very strong and prevents its removal in subsequent processing of the tow.

Cellulose acetate filaments melt at about 240 C. Two polymers that may be used for this invention are illustrated bv polyvinyl acetate, which melts at about 60 C., and half-second butyrate, which melts at about C. Tests indicate that both of these materials will bond to the surface of cellulose acetate and still retain the identity of the fine particle of the polymer as incorporated in the slurry. About one minute is sufficient to bond polyvinyl acetate particles to acetate filaments in an air atmosphere at a temperature of 120 C. It requires about 180 C. to bond half-second butyrate particles.

For assistance in a further understanding of the instant invention, reference is made to the attached drawing forming a part of the present a plication.

In the attached drawing FIG. 1 comprises a semidiagrammatic side elevation view somewhat in the nature of 'a flow sheet of the over-all apparatus combination that maybe used in carrying out my process.

'In the attached drawing a substantially conventional spinning cabinet is shown at 2. The spinning cabinet would be provided with suitable air inlets at 3 and 4 for example and an outlet for air and solvent as at 6. A spinneret 7 is positioned in the top of the spinning cabinet, which spinneret may be of usual construction or may be provided with smaller orifices particularly when producing the relativelv fine denier filaments of the present invention.

The freshly spun filaments leave the bottom of the cabinet as at 8. The filaments thus leaving the cabinet contact rotating roll 9 which is bathed in trough 10.

' roll at the bottom of the spinning cabinet.

6 Trough 10 contains the polymer slurry of the present invention, which slurry it is desired to apply to the freshly spun filaments.

The plurality of filaments thus treated with slurry are conducted around Godet roll 11, a standard item of equipment. This group of filaments 12, usually 50 or more, for the preparing of a tow, would be combined with a number of other groups of filaments illustrated by 13 and 14 similarly prepared in other spinning cabinets positioned in close proximity to the cabinet 2 being described.

That is, depending upon the denier of the tow which it is desired to produce, the number of filaments being spun in each cabinet and the like factors would control the particular number of spinning cabinets that would be operated together. In making certain tows it might be desirable to operate up to 100 cabinets together to produce the desired number of filaments for making the tow.

The combined groups of the several filaments from the several spinning cabinets are fed into a crimper 16 as at point 17. The particular crimper used is not a limitation on the present invention and may comprise any suitable structure that will impart a uniform crimp of more than four crimps per inch to the bundle of filaments. In general I would prefer imparting a crimp of the order of 912 per inch and may in some instances crimp as high as 18 crimps per inch. Because of the application of the slurry in liquid form as above described, there is no difficulty encountered at this point of the polymeric additive of the present invention coming off the filaments. However, I have found that the liquid aqueous slurries of the present invention actually to some extent may facilitate the crimping operation.

The crimped filaments are then discharged from crimper 16 onto any suitable type of conveyor 18 which carries the crimped filaments through drier 19. As will be observed from the further description, the drier not only functions in a normal manner to dry the filaments, but the heat imparted at this point serves to convert the slurry into additives that are strongly bonded to the surface of the filaments.

The roughened filaments thus formed into a crimped tow are discharged from the end of the drier into some suitable form of package as into a bale as generally indicated at 20.

A further understanding of my invention will be had from a consideration of the following examples which illustrate the carrying out of certain preferred embodimerits.

Example I A water suspension containing about 1'0-20% polyvinyl acetate is prepared having a particle size in the range of 5-20 microns. This suspension is applied to a conventional yarn at the bottom of the spinning cabinet as shown in the drawing so that about 10% of the yarn weight would be polyvinyl acetate. The yarn is formed by extruding acetate dope through a jet of many small orifices into an air atmosphere in a spinning cabinet.

The filaments formed by the evaporation of the aceton solvent from the dope are collected by means of a Godet The emulsion is applied by passing the yarn over the surface of a rotating roll partially submerged in a reservoir of slurry.

After the application of the emulsion the strand of filaments is passed through a crimper and deposited on a moving belt, which passes through a tow drier. The temperature of the yarn in the tow drier is raised to about 50-70 C. This softens the polyvinyl acetate particles and causes them to bond to the acetate filaments. This tow can then be baled or otherwise packaged or processed into a filter tip by the standard methods without beating or dusting off of the small particles. The method is applicable to all tows produced at present from. 2 denier per filament to 16 denier per filament.

4- Example II A cellulose acetate spinning solution containing 30% cellulose acetate, 1.75% water and 68.25% acetone is,

extruded through a spinneret containing 600/.035 mm. holes into a spinning cabinet containing an evaporative medium of air. The filaments are formed in the spinning cabinet by evaporating the acetone and are collected at the bottom of the spinning cabinet by a Godet roll.

A slurry of polyvinyl chloride (Firestone Exon 654) is applied to the filaments at the bottom of the spinning cabinet, using a roll rotating in a trough containing the slurry. The slurry contains polyvinyl chloride dispersed in small particles of approximately 10-20 microns. The slurry is applied to the yarn at approximately 12% polyvinyl chloride on yarn weight.

The denier of the yarn before addition of the slurry is 1200, which gives a D/F of 2. The yarn is then crimped and passed through a tow drier at 200 C. The polyvinyl chloride becomes soft and tacky at about 120-l50 C. As the yarn passes through the tow drier the surface of the polyvinyl chloride particles softens and they stick to the acetate filaments. The approximate time of the tow in the drier is three minutes.

When this crimped tow is stretched and opened prior to making a filter rod, the polyvinyl chloride particles do not come off. When similar tow is processed without the application of additive in accordance with the present invention, many of the particles dust off of the filaments.

Evaluation of filter plugs made from a 50,400 denier tow containing the heat-set polyvinyl chloride particles prepared as set forth above, gave a tar removal of 51%, with a pressure drop of 2.95 inches of water on a 15 mm. plug.

In the above examples I have described the application of the slurry or emulsion of the polymeric additive of the present invention to filaments prepared by conventional spinning procedures. That is, the spinning solutions contained a content of cellulose acetate of the order of 30%, which cellulose acetate had an intrinsic viscosity in the range of 1.51.6. Such types of spinning solutions are satisfactory for readily producing filaments having a denier per filament of greater than 2.

In accordance with a special embodiment of the present invention it is contemplated that relatively fine denier filaments be prepared such as filaments of a denier substantially below 2. In order to accomplish this, it has been necessary to develop a new procedure for making such fine denier filaments. I have found that relatively fine denier filaments of a denier below 2 may be quite readily produced by using a cellulose acetate of an increased intrinsic viscosity and in certain proportions in the spinning solution as will be explained in detail below.

The formula showing the relation of the variables controlling denier per filament is set forth below and it can be seen that all the variables are relatively fixed except the concentration of cellulose acetate in the spinning solution:

(dope percent solids) (dope density) (orifice diameter) spinning draft DIF=K The variation in dope density with cellulose acetate concentration and temperature is relatively insignificant. With presently used acetate, the minimum concentration thereof usually used is 26.5%. A reduction of the concentration below this point results in a spinning solution 1.6. By increasing the I.V. to 2.0 a spinning dope can be made with a cellulose acetate concentration of 22.5% having a solution viscosity of 180 poises at an extrusion temperature of 60 C. A yarn having one denier per filament can be spun from this dope, using a GOO-hole spinneret having an orifice diameter of .035, without exceeding the maximum spinning draft of about 1.8.

Increasing the average molecular weight of the cellulose acetate to give an I.V. of 2.3 gives a spinning dope having 17.5% CA at the minimum extrusion viscosity of 180 poises. A filter tow having .8 D/F can be spun from this dope using a 600-hole spinneret with .035 mm. orifices, without exceeding my preferred maximum spinning draft of 1.8. The term intrinsic viscosity as an indication of the average molecular weight of cellulose acetate was developed by Mr. E. O. Kraemer. His publication on this subject appears in Industrial and Engineering Chemistry of October 1938, and the term intrinsic viscosity is well known.

Illustrations of making several very fine denier filaments and the roughening of the surface thereof will be set forth in the following examples:

Example III A cellulose acetate spinning solution is prepared con taining 22.0% cellulose acetate, 1.6% water and 76.4% acetone. The acetate has an intrinsic viscosity of 2.08 and contains 40% acetyl. The viscosity of the solution is 1200 poises at 30 C. as measured by the falling ball method. After thorough filtration the solution is extruded through a spinnerette having 900 orifices of 0.035 mm. diameter. The extrusion temperature of the solution is 50 C. which gives an extrusion viscosity of 250 poises. The yarn is cured in a spinning cell using air at a temperature of 100 C. in both the top and the bottom of the cell. The filaments thus formed are taken up on a Godet roll at the bottom of the cell at a speed of 600 meters per minute. Before reaching the Godet roll the yarn passes over a roll rotating in a slurry containing 50% polyvinyl chloride, as in Example II. Yarn denier before application of the slurry is 900, which gives a D/F of 1.0. The slurry is applied to give approximately 12% PVC based on yarn weight. The yarn is then crimped in 24,000 denier tow and passed through a tow drier at 200 C. for 3 minutes. The PVC particles melt on the surface and fuse to the filaments. The PVC particles do not dust oif when the tow is processed into filter plugs. Filter plugs 15 mm. in length made from this tow will remove 5560% of the tobacco tar in cigarette smoke with a pressure drop of 3.0".

Example IV A cellulose acetate spinning solution is made up at 17.5% CA, 1.6% water and 80.9% acetone. The acetate has an intrinsic viscosity of 2.3 and contains 40% acetyl. The viscosity of the solution is 180 poises at an extrusion temperature of 60 C. as determined by the falling-ball viscosity method. After thorough filtration the solution is extruded through a 600-hole spinnerette with orifice diameters of .035 mm. The filaments are cured in a spinning cell the same as in Example III. A polyvinyl chloride slurry is applied to the tow in a concentration of approximately of tow weight. The yarn denier before application of the slurry is 480 which gives a D/F of 0.8. The tow is crimped and heat bonded the same as in Example III.

It is believed apparent from the foregoing that there has been provided a relatively simple, economical procedure for roughening the surface of filaments which procedure is particularly advantageous in that the procedure does not involve dry, dusty particles. Also, the resultant roughened surface filaments comprise a product wherein the particles are more strongly bonded to the surface of the filaments than has heretofore been possible by prior art procedures. Although the present invention is particularly adapted to cellulose filaments of a denier per filament below 16, which filaments have a crimp in excess of 4 crimps per inch as fully illustrated in the above examples, my method may be applied to other types of filaments using other slurries of polymeric additives. For example, freshly prepared filaments may be treated with slurries of polymeric materials such as polyvinyl acetate, polyvinyl alcohol, styrene 'butadiene copolymers, cellulose acetate butyrate and polyethylene.

Although the slurry may be quite conveniently applied by the roll method illustrated in the attached drawing, other methods of applying a slurry such as by spraying may be used.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected Within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A method of making a roughened tow comprised of several thousand continuous filaments which have on their surface a polymeric material for giving such roughened effect, which comprised dry spinning a cellulose ester spinning composition into a plurality of filaments, applying to these freshly spun cellulose ester filaments a slurry of a polymer material, said slurry being characterized in that a substantial portion of the polymer material is in the form of particles of a size less than 30 microns and the polymer material has a melting point below the melting point of the filaments, passing the filaments thus treated with the slurry containing said particles through a crimping process whereby the filaments are crimped, passing the filaments through heating and drying wherein the heating is sufiicient to cause the particles of polymeric material of the slurry to firmly bond to the filaments.

2. A process in accordance with claim 1 wherein the filaments from a plurality of cabinets and having said polymer slurry particles on the surface are gathered together, crimped, heated to bond the particles to the filaments and then packaged.

3. A process in accordance with claim 1 wherein the slurry is comprised of water containing a compound from the group consisting of polyvinyl chloride and polyvinyl acetate.

4. A process in accordance with claim 1 wherein the filaments having slurry particles bonded thereto are packaged in a bale.

References Cited in the file of this patent UNITED STATES PATENTS 2,034,008 Taylor Mar. 17, 1936 2,085,293 *Bufiington June 29, 1937 2,090,669 Dreyfus et al. Aug. 24, 1937 2,133,322 Cupery Oct. 18, 1938 2,368,948 Stallings Feb. 6, 1945 2,657,973 Johnson et al Nov. 3, 1953 2,768,870 Drisch et al. Oct. 30, 1956 2,839,354 Moelter June 17, 1958 2,843,502 Fay July 15, 1958 2,852,332 Gaebel et al Sept. 16, 1958 2,854,985 Watkins Oct. 7, 1958 2,858,186 Frost Oct. 28, 1958 2,862,783 Drurnrnond Dec, 2, 1958 

1. A MEHTOD OF MAKING A ROUGHENED TOW COMPRISED OF SEVERAL THOUSAND CONTINUOUS FILAMENTS WHICH HAVE THEIR SURFACE OF POLERMIC MAMTERIAL FOR GIVING SUCH ROUGH ENED EFFECT, WHICH COMPRISES DRY SPINING A CELLULOSE ESTER SPINING COMPOSITION INTO A PLURALITY OF FILAMENTS, APPLYING TO THOSE FRESHLY SPUN CELLULOSE ESTER FILAMENTS A 